Policy-driven versus Evidence- based Conservation: A Review of Political Targets and Biological Needs

I has been called “politically correct” (Noss 1996), “politically convenient” (Solomon et al. 2003),“politically achievable” (WCED 1987), “bold but credible” (Miller and McNeely, as quoted by Pressey and colleagues [2003]), a “heroic accomplishment”(Soulé and Sanjayan 1998), and “appropriate...because it’s achievable” (Sierra et al. 2002). It has just as often been labeled as “arbitrary” (Wright et al. 2001), “inadequate” (Rodrigues and Gaston 2001),“completely inadequate” (Solomon et al. 2003), “hopelessly inadequate” (Margules et al. 1988), and “a paltry tithe”(Soulé and Sanjayan 1998). The 10 percent conservation target or goal is an arbitrary value, but one that has gained considerable popularity in the past two decades, without evidence of biological substance or conservation merit. References to a 10 percent (or, alternatively, 12 percent) target are widespread in the literature, as if it were established as meaningful. These percentage targets, or goals, refer to the proportion of the earth’s surface that is ostensibly required to meet conservation goals. As they are usually interpreted, if at least 10 or 12 percent of a region has been designated as protected, the goal has been achieved. Although such goals were considered bold when first proposed (Soulé and Sanjayan 1998), results from conservation assessments and plans throughout the world now suggest that generic a priori targets of 10 and 12 percent, without consideration of on-the-ground biology, may be an unfortunate example of good intentions gone awry. Species vary widely in their space requirements. For instance, the area required for a viable population of grizzly bear (Ursus arctos) is much larger than for a cliff chipmunk (Tamias dorsalis). In addition, the areas required to maintain minimally viable populations may vary by orders of magnitude from those required for ecologically or evolutionarily viable populations (Peery et al. 2003, Soulé et al. 2005). Even so, the relationship between habitat loss and species loss (i.e., species–area curve) is well established (Williams 1943). Given this relationship, at the 10 percent target level of habitat protection, 50 percent of species could be lost.